Electrical control mechanism for oil and other fuel-burning equipment



July 21, 1925. 1,546,640

. F. FISCHER ET AL ELECTRICAL CONTROL MECHANISM FOR OIL AND OTHERFUEL'BURNING EQUIPMENT Filed April 11, 1925 3 Sheets-Sheet 1 Fig.1

W TNESSE INVENTORS July 21,1925.

F. FISCHER ET AL ELECTRICAL CONTROL MECHANISM FOR OIL AND OTHER FUELBURNING EQUIPMENT 3 Sheets-Sheet 2 Filed April 11, 1925 Fig. II

W- INVENTORIS Wffi flat July 21; 1925.

F. FISCHER ET AL ELECTRICAL CONTROL MECHANISM FOR OIL AND OTHER FUELBURNING EQUIPMENT Filed April 11 1925 s Sheets-She et s PatentedJuly 21,1925. T

1 UNITED STATES PATENT; OFFICE.

FRANK FISCHER, F LARCHMONT, NEW YORK, AND ARNOLD F. VAN FELT, OF INTER-I LAKEN, NEW JERSEY.

ELECTRICAL, oonprnor. MECHANISM T 0 all whom it may concern.

' Be it known that we, FRANK FISCHER and ARNOLD F. VAN PELT, citizens ofthe United States, residing at Larchmont, in the county of WVestchesterand State of New .York, and at Interlaken, inthe county of MonmouthandState, of New Jersey, respectively, have invented certain new and usefulImprovements in Electrical Control Mech nection with burners fordomestic use, hecause the control is fully electrical and does notdepend upon unreliable drip-pans or similar mechanisms to shut down thee uipment in case of failure to ignite; an because it does notrequireexpert attendance. The general object of this invention is toprovide a fully automatic control which is safe, economical, andinfallible for governing oil or similar fuel burning equipment. Onespecific object is to automatically start the fuel-supply motor and theignition system of the burner when the circuit is closed by any meanssuch as a manually operated switch or a thermostat, boiler control, orsimilar device. The operation of these devices is well known and iscontrolled by the temperature of the place to be heated, or by thetemperature. or pressure of the boiler or furnace. v

Another object is to automatically stop the fuel-supply motor and theignition system of the burner whenthecircuit is opened by any means suchas a manually, operated switch, 'or a thermostat, boiler-control orsimilar device. P I 0 Another object is to shut off the ignition systemin a predetermined. time after the burner is lighted.

FOB OIL AND OTHER FUEL-BURNING Ecum- MENT.

Application filed April 11,1925. Serial No. 22,499.

system again automatically if the burner should go out for any reasonwhatsoever, other than the complete shutdown of the burner.

Another object is to shut down the fuelsupply motor and the ignitionsystem automatically in a predetermined time if the oil or other fuelhas failed to ignite. In order to prevent the depositing of an excessiveamount of unburned fuel in the combustion chamber, the predeterminedtime of shut down may be set from 30 seconds to 10 minutes-as desired. I

Another object isto shut down the fuelsu'pply motor and ignition systemautomatically upon the failure of any one of the elements in the controlcircuit in a predeter- 'mined time (as above noted).

Another object is to shut down the burner and ignition systemautomatically if the fuel supply should fail.

Another object is to prevent the 'burner from auton'iatically startingafter 'it has shut itself down because of failure to obtain ignition, orfailure of any of the elements in the circuit, or failure of the fuelsupply as aforesaid,-said shut-down to be maintained until the equipmentis inspected and the control manually reset.

Other objects will hereafter appean.

The nature and scope of this invention are more fully explained in thefollowing description taken in connection with the accompanying drawingsforming part of this specification, in which:

Fig. I is a diagram of our control mech anism adapted to alternatingcurrent, and

having a low voltage thermostat and boilercont-rol properly connected toour circuit.

Fig. II is a diagram of our control mecha nism for operating on director alternating current without the low voltage element of the -circuit.The thermostat and boiler-control shown are designed for operation onthe normal lighting or power circuit.

Fig. III shows an oil-burning furnace equipped with our controlmechanism.

Similar numerals refer to similar parts \throu hout the several figures.

60. Another object -is -t0 start the ignition In ig."I, 1 and 2 arealternatingcurrent 2 being preferably the grounded side of the line, ifthe line is grounded.

3 and 4 are terminals of electric motor 5.

which drives the pump or other apparatus supplying fuel to the burner. 6is a solenoid with terminals 7 and 8, and movable core 9, although arotary form of motor could readily be substituted here for performingthe ndechanical work of operating a valve, switch, or other ignitionapparatus. 6 will therefore be referred to hereafter as theignition-motor,

10 is a gas valve operated by ignitionmotor 6. v

11 to 21 inclusive comprise a time-limit cut-out. A time-limit cut-outpermits an electric current of .a given strength to fiow through it foronly a limited period of time.

In this particular time-limit cut-out, 11 is a resistance wire orheating coil; 12 is a piece of thermostatic. metal with oneend fastenedrigidly at 13 and the other end bearing against brass member '14 whichis pivoted at 15.

,Thermostatic metal 12 is superimposed above the resistance wire orheating-coil 11 and bends upward when heated, as indicated by dottedlines 12. Member 14 is connected through flexible lead 16 to coil 11,and carries contactor 17 which is held against contactor '18 by the endof thermostatic metal 12. 19 is a compression spring bearing againstbrass member 14 at one end andagainst fixed piece 20 at the other.Compression spring 19 provides a quick break between contactors 17 and18 when thermostatic metal 12 has been heated by coil 11, and has movedabove the end of member 14 as indicated by broken lines 12.

21 is a. re-setting member which passes through a hole in fixed piece20, through compression spring 19, and fastens to member 14. Its purposeis to enable member 14 with its contactor 17, to be pulled over againstcontactor 18 so as to allow thermostatic metal 12 to spring downward andreset against member 14 when thermostatic metail 12 has cooledsufiiciently.

22 to 37 inclusive are parts of a commercial relay, a thermostat, and atransformer, all interconnected for the'purpo'se of automaticallyclosing and opening the power circuit, at predetermined temperatures orpressures. 22 is the rela armature, carrying an insulated hook forlifting relay arms 23 and 24.

25 and 26 are contactors on the relay in the main power circuit. 27 and28 are low voltage contactors. 29 is an electro-magnet. 30 is aresistance coil. 31,32 and 33 are contactor points on a low voltagethermostat. 34 and 35 are the terminals of the secondary winding of atransformer; 36 and 31 are terminals of primary winding of the saidtransformer. 38 and 39 are terminals of a switch or similar deviceusually connected mechanically or electricall in some suitable manner tothe boiler Or furnace or apparatus which contains the burner.

40 is a fuse which is connected in series with a shunt box which isindicated by numerals 41 to 46 inclusive, both of which are shuntedaround the ignition-motor 6 and heating coil 11.

The shunt-box, which constitutes part of our invention, acts as amonitor over the time-limit relay, preventing it from functioning orpermitting it to function according to whether the burner is ignited ornot ignited, respectively. This shunt-box consists of a fixed insulatedmember 41 through which is passed adjusting screw 42 carrying contactor43. 44 is a contactor fastened to thermostatic metal 45 which in turn isfastened rigidly to fixed insulated member 46..

The shunt-box is conveniently placed in the stack of the furnace, but itcan be put in vmany places near the furnace or boiler and.

still be effective. Other materials which expand or become otherwisedistorted by heat, may be substituted in the place of the thermostaticmetal members 12 and 45, although certain commercial metals are usuallyconsidered most practical for this purpose.

Hereafter, 6 to 9 will be referred to as an ignition-motor; 11 to 21will be referred to as atime-limit cut-out; 22 to 29 will be referred toas a relay; 31 to 33 will be referred to as a thermostat; 34 to 37 willbe referred to as transformer; 38 to 39 will be referred to as aboiler-control; and 41 to 46 will be referred to as a shunt-box.

The descriptive name time-limit cut-out explains the function of thiscut-out apparatus; which function is to open an electric circuit passingthrough it, and thereby cut out any other apparatus connected in serieswith it, after the lapse of a certain predetermined time constitutingthe time-limit factor. The operation of the time-limit cutout ishereinafter more fully described.

Fig. II contains no additional parts over Fig, I, but on the other handshows our control circuit without the relay and lowvoltage circuitpreviously described.

Fig. III shows a convenient arrangement of the devices enumerated inwhich:

The solenoid ignition-motor, gas valve, time-limit cut-out, relay,transformer, boilercontrol switch, and fuse may be considered as locatedon a suitable panel-board all enclosed in a metal case or panel-box.These parts are enlarged in the drawing to enable the circuit to betraced more readily.

Thefuel-supply motor 5 and pump 47 are placed convenlently .'withrelation to the boiler or furnace 48.

The shunt-box is most conveniently placed in the stack 49 of the furnace48. The

'of the boiler if preferred.

57 may be actuated thermostat isplaced'in the particular room or placethe temperature of which is to be controlled.

Oil supply tank is connected by means of pipe 51 with the pump 47 whichentrains. oil from tank 50 and air through port 52; and after mixingthem in the proper. proportions, discharges them through burner supplypipe 53 and nozzle 54 into the firebox of the furnace.

Gas pilot flame 55 is fed through gas pipe 56 and gas valve 10, thelatter being controlled b solenoid ignition-motor 6.

In Fig. I I the boiler-control is shown as a diaphragm piston 57connected, through Weighted lever 58 and chain or cable 59 passing overpulleys 60 and 61, with switch 62; although the whole boiler-controlapparatus may be installed as aunit on the top The diaphragm piston bythe pressure of steam in the boiler, or by the pressure of any trappedfluid which expands when heated. In the latter case the boiler-controlmay be considered as operated by the temperature, rather than thepressure of the boiler.

The operation of our oil-burner control mechanism is as follows:

The power current is always presumed to be on lines 1 and 2.

Assuming vthat the temperature or pressure of the boiler or furnace isbelow a predetermined point, above which it is to be 'maintained,'thelower temperature contacts 31 and 32 of the thermostat andboiler-control leads 38 and 39 will be closed. The transformer, usuallyof the type to trans form the normal 110 volt lighting current to 1 alower voltage, usually 24 volts, is energized, and is therefore in aposition to sup- I ply current to the relay. At the predeterminedtemperature, the thermostatic member 31 of the thermostat makes contactwith 32 which energizes the magnet 29 which in turn pulls up thearmature 22 and the adjacent contactor arms 23 and 24 which in turnclose contactors 25 to 26 and 27to 28. The closing'of contactors 27 and'28 magnet ically locks the armature 22 in place and the closing of. themain line contactors 25 and 26 completesthe circuit for the current totravel from the supply line 2, through the fuel-supply motor 5, throughthe solenoid 6,

through the time-limit cut-out, through the maincontactors 25' and 26 ofthe relay, and back'to line 1.

This forms a series circuit inwhich'the breaking of any of the lines orvconnections in theicir'cuit would cause the entire circuit to becomeopen and therefore inoperative.

The instant the relay picks up, the motor 5 starts, whichnin'turnstartsthe pump and sprays oil into the furnace; thexsolenoid 6 is energized,which forces plunger 9 upward is thereby ignited.

started in operation by the thereby opening the gas valve 10 (or anyother similar device) and the'heating coil 11 of the time-limit cut-outbegins to heat up. If nothing further takes place, the heatgenerated inthe coil 11 of the time-limit cut-out will cause thermostatic metal 12to bend upward and pass the end of member 14. This in turn will allowcompressionspring 19 to force member 14 out of its position and breakcontactors 17 and 18 which open the circuit and thereby de-energize the"solenoid 6 and the motor 5. The plunger 9- falls to its normal positionthereby closing the gas valve 10 (or other mechanism) and thefuel-supply motor stops, thereby stopping the fiow of oil into theboiler or.

furnace.

However, when the motor 5 is started and.

thesolenoid 6 opens the gas valve 10, it exands the pilot'light 55, Fig.III which is ein'g fed by this gas valve,

oil which is being sprayed into the furnace At a predetermined timeafter ignition has taken placethermostatic metal 45 in the shunt-box inthe stack 49 starts to move and closes contactors 44 and 43. This hasthe effect of.shunting out the solenoid 6 and the heating coil 11 in thetime-limit cut-out.

Shunting out the solenoid in this manner so that the fuel allows the gasvalve 10 to close thereby cone.

tracting the pilot to its normal position.

Shu'nting out the heating coil 11 permits it to cool down and there orethermostatic member 12 does not move and contactors 17 and 18 arethereby unable to be forced apart by compressing spring 19, and theburner continues to function normally.

If the gas pilot, which is expanded by the solenoid 6 pressing againstthe gas-valve 10, has'for any reason been blown out, or the electricorother ignition system which is solenoid 6, fails to operate, sprayedinto the furnace but not ignited. Under these circumstances thethermostatic metal 45 of the shunt-box would receive no heat, andconsequently would not move .to bring contactors 43 and 44 together, sothat the current taken. to operate the motor 'wouldcontinue to passthrough; the timelimit cut-out (particularly through the heating coil11) and through the solenoid 6. The heat generated in the resistancewire of heating coil 11 under these circumstances would be suflicient,in a predetermined time, to cause thermostatic member 12 to move upwardallowing compression spring 19 to 'act and break the contact at 17 and18 therebyopen the circuit and shut down all of the apparatus.

If the burner should be functioning nor:- mally hausted, combustionwould of course cease. This would allow thermostatic metal 45 in and theoil supply should become exthe shunt box to cool and assume its normalposition, opening contactors 43 and 44. This would then permit all ofthe current which is being taken by the motor to pass through the coil11 of the time-limit cut-out and through solenoid 6a This would have theeffect of heating coil 11, which would in turn cause thermostatic member12 to move up out of the way of member 14, and in a predetermined timecircuit would be open between contactors 17 and 18, and all of theapparatus would shut down.

If it should happen that contactors 43 and 44 should stick togetherfreeze, and the burner then be started up with these contactors closed,the. larger starting current of the motor 5, in attempting to take thepath of least resistance, would blow the fuse 40 which is in theshunting circuit, thereby opening the shunt circuit. The coil 11 of thetime-limit cut-out would immediately be energized, and inasmuch as theshunt circuit is open, the motor 5 would shut down in a predeterminedtime as heretofore explained. The precise location and resistance ofthis fuse in the circuit is of considerable importance in thisinvention.

It is to be understood that this invention is not limited to the exactform or arrangement of parts shown in the accompanying drawings but thatmodification therein may be made without departing from the spirit ofthe invention as defined by claims.

We'are aware that prior to this invention,

relays solenoids and various forms of thermostatic controls have beenused commerciall for sundry purposes, and do not claim tiiese individualcircuits in detail. What we do claim and desire to secure by LettersPatent is 1. In an electrical control mechanism for burners, thecombination of a fuel-supply motor, an ignition motor, and a time-limitcut-out tending to de-energize the motor in a predetermined time, allconnected in series in an electric circuit, and means for preventing thecut-out from tie-energizing the fuel-supply motor when the burner isignited. J

2. In an electrical control mechanism for burners, the combination of a"fuel-supply motor, a heat-coil and a pair of contactors, all connectedin series, a yielding means for separating the contactors, and athermostat metal member inproximity to the heat-coil to hold thecontactors together when said member is cool, but to permit thecontactors to separate and de-energize the motor after said member isheated, and means for shunting out the heat-coil when the burner isignited.

3. In an electrical control mechanism for burners, the combination of a,fuel-supply motor, an ignition motor, a heat-coil and a 'ture-actuateddc-energize the motors when said member is heated, and means forshunting out the heatcoil and the ignition-motor when the burner isignited. 1

4. In an electrical control mechanism for burners, the combination of afuel-supply motor, an ignition-motor, a heat-coil, and a pair ofcontactors, all connected in series, a yielding means for separating thecontactors,'and a thermostat metal member in proximity to the heat-coilto hold the contactors together when said member is cool, but to permitthe contactors to separate and de-energize the motors when said memberis heated, and means for shunting out the heat-coil when the burner isignited.

5. In an electrical control mechanism for burners, the combination of afuel-supply motor, an ignition-motor, a heat-coil, and a pair ofcontactors, all connected in series, a yielding means for separating thecontactors, and a thermostat metal member in proximity to the heat-coilto hold the contactors together when said member is cool, but to permitthe contactors to separate and de-energize the motors When said memberis heated, and means for shunting out the ignition-motor when the burneris ignited.

6. In an electrical control circuit for burners the combination of afuel-supply motor, an ignition-motor, and a time-limit cut-out allconnected in series, a temperature actuated shunt-box forming whenclosed by heat from the burner, a shunt 'circuit around theignition-motor and time-limit cut-out so as to substantially de-energizethe ignition-motor and the time-limit cut-out.

7. In an electrical control circuit for burners the combination of afuel-supply motor, an ignition-motor and a time-limit cut-out allconnected in series, a temperature actuated shunt-box forming whenclosed by heat from the burner, a shunt circuit around the ignitionmotor so as to substantially deenergize the ignition-motor.

8. In an electrical control circuit for burners the combination of afuel-supply motor, an ignitionmotor and a time-limit cut-out allconnected in series, a temperashunt-box forming when closed by heat fromthe burner, a shunt circuit around the time-limit cut-out so as LOsubstantially de energize the time-limit cutout.

9. In an electrical control circuit for burners, the combination of afuel-supply motor, an ignition-motor, and a time-limit cut-out allconnected in series, and means cut-out, all connected in series inan-electric' for shunting out and thereby substantially de-energizing"the time-limit cut-out and the ignition motor when the burner isignited,

10. In an electrical control circuit for burners, the combination of afuel-supply motor, an ignition-motor, and a time-limit cut-out allconnected in series, and means for shunting out the ignition-motor whenthe burner is ignited.

11. In an electrical control circuit for burners, the -combination of afuel-supply motor, an ignition-motor, and a time-limit cut-out allconnected in series, and means for shunting out the time-limit cut-outwhenthe burner is ignited.

12. In an electrical control circuit for burners the combination of afuel-supply motor, an ignition-motor, and a time-limit circuit, atemperature-actuated shunt-box and a fuse connected in series with eachother but forming, when the shunt-box is closed by heat from the burner,a shunt or short circuit around the ignition-motor and the time-limitcut-out so as to substantially de-energize the ignition-motor and thetime-limit cut-out.

13. In an electrical control circuit for burners, the combination of afuel-supply motor, an ignition-motor, and a time-limit cut-out, allconnected in series in an electric circuit, a temperature actuatedshuntbox and a fuse connected in series with each other but forming,when the shunt-box is closed by heat from the burner, a shunt orition-motor so motor. p p

14:. In an electrical control circuit for burners, the combination of afuelssupply motor, an ignition-motor, and a time-limit cut-out, allconnected in series in an electric circuit, a temperature-actuatedshuntbox and a fuse connected in series with each other but forming,when the shunt-box is closed by heat from the burner, a shunt or shortcircuit around the time-limit,cut-out soyas to substantially de-energizethe time limit cut-out.

15.- In an electrical control circuit for I burners the combination of afuel-su ply motor, an ignition motor, and a time- 1m1t cut-out,allconnected in series in an electric circuit, a temperature actuatedshunt-box and a fuse connected 1n series with each other but forming,when the shunt box is closed by heat from the burner, a shunt or shortcircuit around the ignition-motor and the time-limit cut-out, the fusebeing-designed to carryits shunted proportion of the currentnecessary torun but not to start the fuel-supply motor. 7

16. In an electrical control circuit for burners the combination of afueLsupply motor, an ignition-motor, and a time-limit cut-out, allconnected in series in an electric circuit, a temperature actuatedshunt-box and a fuse connected in series with each other but forming,when the shunt box is closed by heatfrom the burner, a shunt or shortcircuit around the time-limit cut-out,

the fuse being designed to carry its shunted proportion of the currentnecessary to run at not to start the fuel-supply motor.

17. In an electrical control circuit for burners the combination ofafuel-supply motor, an ignition-motor and a time-limit cut-out, allconnected in series in an electric circuit, a temperature actuatedshuntbox and a fuse connected in series with each other but forming,when the shunt, box is closed by heat from the burner, a shunt or. shortcircuit around the ignition-motor, the.

fuse being designed to carry its. shunted proportion of the currentnecessary to run but not to start the fuel-supply motor.

18. In an electrical control mechanism for burners, the combination of afuel-supply motor, an ignition-motor, and a time-limit cut-out, allconnected'in seriesin an electric circuit, a temperature-actuatedshunt-box consisting of a pair of contactors and a thermostatic metalmember located in proximity to the burner and arranged to open thecontactors when said member is cool and to close them when said memberis heated,

said shunt-box being so connected as to shunt {out or 'short' circuitthe ignitionmotor and the time-limit cut-out when the burner is ignited.i r

19. .In an electrical control mechanism for burners, the combination ofa fuel-supply motor, an ignition motor, and a time-limit cut-out, allconnected in series in an electric circuit, a temperature-actuatedshunt-box consisting of a p'air'of contactors and a thermostatic metalmember located in proximity to the burner and arranged to open 1' thecontactors when said member is cool and to close them when said memberis heated, said shunt-box being so connected as to shunt out or shortcircuit the ignition-motor when the burner is ignited. v

20'. In an electrical control mechanism for burners, the combination ofa fuel-supply motor, an ignition-motor, and a timelimit cut-out, allconnected in series in an electric circuit, a temperature-actuatedshunt-box consisting of a pair of contactors and a thermostatic metalmember located in proximity to the burner and arranged to open thecontactors when said member is cool and to close them when said memberis heated, said shunt-box being so connected as to shunt out or shortcircuit the time-limit cut-out when the-burner is'i ted.

21. In an e ectrical control circuit for burners, the combination of afuel-supply motor, a time-limit cut-out, and an ignitionmotor, allconnected in series, means operated by said ignition-motor for ignitingthe fuel supplied by said fuel-supply motor.

22. In an electrical control circuit for burners, the combination of afuel-supply motor, a time-limit cut-out, and an ignitionmotor, allconnected in series, means operated by said ignition-motor for ignitingthe fuel supplied by said fuel-supply motor, and other means forpreventing said cut-out from de-energizing the fuel-supply motor whenthe burner is ignited.

23. In an electrical control circuit for burners, the combination inseries, of a fuelsupply motor, an ignition-motor, a timelimit cut-outconsisting of a heat-coil, a fixed contactor, and a movably mountedcontactor connected in series, a yielding means tending to separate thetwo contactors. a thermostatic member in proximity to the heat-coil andarranged to hold the contactors together when said member is cool, butto allow them to separate when warmed by the heat-coil, and manuallyoperated means for re-closing said contactors after said thermostaticmetal member has cooled, and other means for preventing said contactorsfrom separating when the burner is ignited.

24. In an electrical control mechanismfor burners the combination, in aseries circuit, of a fuel-supply motor, an ignition-motor, a time-limitcut-out, and a thermostat operated means for opening and closing thecircuit between desired limits of temperature, a temperature-actuatedshunt-box forming a shunt circuit around the ignition-motor and thetime-limit cut-out so as to shunt out the ignition-motor and thetime-limit cut-out when the burner is ignited.

25. In an electrical control mechanism for burners the'combination, in aseries circuit, of a fuel-supply motor, an ignition-motor, a time-limitcut-out, and a thermostat operated means for opening and closing thecircuit between desired limits of temperature, a temperature-actuatedshunt-box forming a shunt circuit around the ignition-motor so as toshunt out the ignition motor when the burner is ignited.

26. In an electrical control mechanism for burners the combination, in aseries circuit, of a fuel-supply motor, an ignition-motor, a time-limitcut-out, and a thermostat operated means for opening and'closing thecircuit between desired limits of temperature, a temperature-actuatedshunt-box forming a shunt circuit around the time-limit cut-out so as toshunt out the time-limit cut-out when the burner is ignited.

27. In an electrical control mechanism for burners the combination, in aseries circuit, of a fuel-supply motor, an ignition-motor, a time-limitcut-out, and a thermostat operated means for opening and closing-thecircuit between desired limits of temperature, a temperature-actuatedshunt-box and a fuse in series therewith forming a shunt circuit aroundthe ignition-motor and the timelimit cut-out.

28. In an electrical control mechanism for burners the combination, in aseries circuit, of a fuel-supply motor, an ignition-motor, a time-limitcut-out, and a thermostat operated means for opening. and closing thecircuit between desired limits of temperature, a temperature-actuatedshunt-box and a fuse in series therewith forming a shunt circuit aroundthe ignition-motor.

29. In an electrical control mechanism for burners the combination, in aseries circuit, of a fuel-supply motor, an ignition-motor, a time-limitcut-out, and a thermostat operated means for opening and closing thecircuit between desired limits of temperature, a temperature-actuatedshunt-box and a fuse in series therewith forming a shunt circuit aroundthe time-limit cut out.

30. In an electrical control mechanism for burners, the combination, ina series circuit, of a fuel-supply motor, an ignition-motor, atime-limit cut-out, and a boiler controlled means for opening andclosing the circuit under predetermined conditions, and atemperature-actuated shunt-box forming a shunt circuit around theignition-motor and the time-limit cut-out.

31. In' an electrical control mechanism for burners, the combination, ina series circuit, of a fuel-supply motor, an ignition-motor, atime-limit cut-out, and a boiler controlled means for opening andclosing the circuit under predetermined conditions, and atemperature-actuated shunt-box forming a shunt circuit around theignition-motor.

32. In an electrical control mechanism for burners, the combination, ina series circuit, of a fuel-supply motor, an ignition-motor, atime-limit cut-out, and a boiler controlled means for opening andclosing the circuit under predetermined conditions, and atemperature-actuated shunt-box forming a shunt circuit around thetime-limit cut-out.

33. In an electrical control mechanism for 1 of a fuel-supply motor, anignition-motor,

a time-limit cut-out, and a boiler controlled means for opening andclosing the circuit under predetermined conditions, atemperature-actuated shunt-box and a fuse connected in seriestherewithand forming a shunt cir-' cuit around the ignition-motor.

35. In an electrical control mechanism for burners the combination, in aseries circuit, of a fuel-supply motor, an ignitionmotor, a time-limitcut-out, and a boiler controlled means foropening and closing thecircuit under predetermined conditions,

a temperature-actuated shunt-box and a fuse connected in seriestherewith, forming a shunt circuit around the time-limit cut-out.

motor, an ignition-motor, a time-limit cut-- out and a main-circuitswitch all connected in series, and a temperature-actuated shunt boxforming when-closed by the heat from the burner, a shunt circuit aroundthe ignition-Inotor. i 1

38. In an electrical control circuit for burners, the combination of afuel-supply motor,.an ignitiommotor, a time-limit. cutout, and amain-circuit switch all connected in ser es, and a temperature-actuatedshunthox forming when closed by the heat from the burner, a shuntcircuit around the timelimit cut-out.

box and a fuse connected in series with each other but forming, whenclosed by heat from the burner, a shunt or short circuit around theignition-motor and the time-limit cutout.

40.- In an electrical control circuit for burners, the combination of afuel-supply motor, an ignition-motor, a time-limit cutout and a 'maincircuit switch all connected in series, 'a temperature-actuatedshunt-box and a fuse connected in series with each other but forming,when closed by heat from the burner, a shunt or short circuit around theignition-motor.

41. In an electrical control circuit for burners. thecombination of afuel-supply motor, ignition-motor, a time-limit cut-out and amain-circuit switch all connected in series, a temperature-actuatedshunt-box with a fuse connected in series therewith, forming when closedby heat 'from the burner, a shunt or short circuit around the time-limitcut-out.

FRANK FISCHER. ARNOLD F: VAN PELT.

